Large centrifugation systems typically use a rotor for holding sample containers which contain the sample to be separated. The rotor is covered by a rotor lid and then placed into an instrument chamber wherein the rotor is spun during centrifugation. Typically, the instrument chamber is evacuated for the centrifugation run to reduce the effects of windage and heat generation.
A problem that sometimes occurs in the operation of these centrifugation systems is that the centrifuge operators, either through haste or inattention, sometimes neglect to tighten down or secure the rotor lids to the rotor assembly. Thus, when the rotor is spun during centrifugation, the rotor lid can be thrown off by the centrifugal force of the spinning rotor. Many problems can result from this, besides the obvious one that the loose lid will damage the rotor and/or centrifuge. The securement of the rotor lid is desirable in order to prevent leakage of the material undergoing centrifugation. This is especially important where toxic and other bio-hazardous materials are concerned. If breakage occurs within the rotor chamber, the material under test may spill and/or release hazardous vapors. Such vapors may release into the atmosphere exposing laboratory personnel to harmful material. Additionally, leakage that escapes the rotor chamber can cause an imbalance in the rotor chamber which can result in spindle breakage or drive failure. Although this problem of failing to secure the rotor lid to the rotor assembly would seem to be preventable by careful attentiveness to laboratory procedures, this problem occurs much more often than would be expected.
In most of the prior art rotor assemblies, the rotor lid rests on top of the rotor body and is secured by a knob on top of the lid that is attached to a bolt or a stem that extends through a bore in the center of the lid and attaches to the rotor body or the centrifuge spindle hub. However, if the lid is not secured by the knob and bolt to the rotor or spindle hub, then the lid just rests on top of the rotor, leading to the problem described above. U.S. Pat. No. 4,850,951 to Cheng et al. discloses a lid retention apparatus for centrifuge rotor covers. In the apparatus, a lid rests on top of the rotor body and a bolt is used to hold the lid on the rotor. The bolt is engaged centrally of a knob on top of the lid and extends through a spacer, a bushing and is held to the lid by a key. The lid is placed on the rotor and the bolt engages with a female threaded aperature in the rotor. The invention comprised cantilevering a bushing from the lid down to the vicinity of the drive hub within the central aperature of the rotor body. This bushing provides a tighter-fit mating part that keeps the lid from easily wiggling out of the rotor.
It is the object of the present invention to provide a rotor lid that is capable of staying on the rotor body even when the lid has not been tightened down or secured.